Process of making indigo products.



NITED STATES PATENT Orricn.

RUDOLF KNIETSOH AND HENRY STALAY ARTHUR HOLT, OF LUDWIGS- I-IAFEN,GERMANY, ASSIGNOR-S TO THE BADISCHE ANILIN AND SODA FABRIK, OF SAMEPLACE.

PROCESS OF MAKING INDIGO PRODUCTS SPECIFICATION forming part of LettersPatent No. 644,326, dated February 27, 1900.

Application filed October 18,1898. Serial No. 693,942. (No specimens.)

To all whom it may concern.-

Be it known that we, RUDOLF KNIETSCH, a subject of the King of Prussia,Emperor of Germany,and HENRY STALAY ARTHUR HOLT, a subject of the Queenof Great Britain and Ireland, both doctors of philosophy, residing atLudwigshafen-onthe-Rhine, in the Kingdom of Bavaria and Empire ofGermany, have invented newand useful Improvements in the Manufacture ofIndigo Products, of which the following is a specification.

Ourinvention consists in a new process for the production of new indigoproducts, including in this term blue coloring-matters belonging to theindigo group and leuco compounds thereof, from new condensation productswhich we have invented and which we obtain from theglycocoll-carboxy-esters of the aromatic series.

It is well known that the simple phenylglycocoll compounds on heatingare readily converted into anhydrides,which are regarded chemically asketo-piperazides, but the production of corresponding compounds fromglycocoll-carboxy-acids has not been successfully accomplished. We havediscovered a method of preparing piperaz'ine derivatives from theglycocoll-carboxy-acids, which can be derived from amido-malonic acid.

The first stage of our new process consists in the production of thesenew piperazine derivatives, and we proceed by heating theglycocoll-carboxy-ester in an indifferent solvent, or even without theuse of a solvent, to a temperature of over 200 centigrade. The reactionproduct is purified in a suitable way-namely, by extracting with anorganic solvent, such as alcohol or acetone, in which the desiredproduct is only slightly soluble.

The new piperazine bodies are insoluble in dilute hydrochloric acid anddilute caustic soda, very slightly soluble in chloroform and methylalcohol, readily soluble in boiling nitro-benzene or aniline. Theirsolution in concentrated sulfuric acid is intensely fluorescent andpossesses a characteristic absorption spectrum.

The second stage of our new process consists in heating a piperazinederivative obtained,as above indicated,with fixed caustic alkalinamely,caustic soda or caustic potash, to which some caustic lime may be added.A yellow to red melt is obtained, which contains indigo leuco bodies,which can either be precipitated by acids and collected as such or canbe converted into a blue coloring-matter of the indigo group bydissolving the melt in water and oxidizing with air or any othersuitable oxidizing agent. p

The following examples will. serve to illustrate the manner in which ournew process can be carried into practical effect. The parts are byweight. 7

Example 1: Production of a new pipe razine derivative frompdra-tolyl-glycocoll-carbozry-di-ethyZ-ester.Dissolve one (1) part ofpara-tolyl-glycocoll-carboxy-di-ethyl-ester in one and a half (1%) partsof petroleum, boiling at a high temperature, and heat to about 250centigrade until the mass is converted into a paste of crystals. Allowto cool, filter with the aid of a filter-pump, wash the residue withligroiue, and then extract with gla cial acetic acid and allow to cool.The reac tion product is of a light yellow color and is then pure enoughfor all practical purposes.

Emample 2: Production of a piperazzfne derioatc'oe frombetccnaphthyZ-glycoc0ZZ=cdrb000g.

di-eth-yZ-ester.-Mix together one (1) part ofbeta-naphthyl-glycocoll-carboxydi-ethyl-ester and two (2) parts ofalpha-chlor-naphtha lene and heat the mixture to a temperature of about260 centigrade, until the melt turns to a mass of crystals. This usuallytakes about one hour. Allow to cool, collect the crystals by filtration,wash with ligroiue, and extract with glacial acetic acid.

The foregoing two examples illustrate the manner in which the firststage of the process can be carried out, using the various aromaticglycocoll carboxy-di-alkyl-esters. If desired, a solvent need not beused in the manner given in the above examples. In that case the meltobtained after heating for some time at the high temperature solidifies.It is powdered, and in order to obtain the desired piperazine compoundpure itis extracted with a solventsu'ch as boiling alcohol, acetone,

benzene, or glacial acetic acid. The extracted mass is allowed to cool,freed from solvent by filtration, and dried.

Example 3: Production of the "indigo products from the piperazt'nederivative. Mix together one (1) part of the tolyl-piperazine derivativeobtained as described in Example 1 and four (4) parts of caustic potashand heat the mixture at a temperature of about 250 to 280centigrade,excluding the air as far as possible. Maintain the temperature until the melt has assumed a deep orange-red color and it canbe seen by testing that the highest yield of coloring-matter is beingobtained. Allow the melt to cool, powderit up, and if it be desired toobtain the indigo product in the form of leuco compound add to it six(6) parts of ice- 'cold dilute sulfuric acid, (containing about productsfrom an aromatic glycocoll-carboxydi-alkyl-ester by heating same to atemperature of above 200 centigrade, and so converting it into apiperazine derivative, then melting this piperazine derivative with afixed caustic alkali, all substantially as described.

2. The process for the production of indigo products from an aromaticglycocoll-carboxydi-alkyl-ester by heating same to a temperature ofabove 200 centigrade, and so converting it into a piperazine derivative,then melting this piperazine derivative with a fixed caustic alkali andlime, all substantially as described.

3. In a process for the production of indigo products from an aromaticglycoooll-carboxydi-alkyl-ester, heating the same to a temperature ofabove 200 centigrade and so converting it into a piperazine derivative.

4. In a process for the production of indigo products melting apiperazine derivative of an aromatic glycocoll-carboxy-d ialkyl-esterwith a fixed caustic alkali, all substantially as described.

In testimony whereof We have hereunto set our hands in the presence oftwo subscribing witnesses.

RUDOLF KNIETSCII. HENRY STALAY ARTHUR- "0LT- \Vitnesses:

ERNEST F. EHRHARDT, J. L. HEINKE.

